You want a tiny mammoth, I want an aquarium sized whale... Where's the line? How long until there's a game show of duck sized horses or horse sized duck?

Real talk? Yes. Miniaturization of animals does not do good things for their health, in general. The systems of animal bodies are finely tuned by natural selection, and mucking with that is how you get dogs that can't breathe because their nose has been bred into the approximate shape of a squished aluminum can. Homeostasis is easy to throw off long-term when you play around with the square-cube law.

See: https://en.m.wikipedia.org/wiki/Allometry#Physiological_scaling